Ecological responses to variable water regimes in arid-zone wetlands: Coongie Lakes, Australia

In dryland rivers, interactions between flow variability and complex geomorphology expose floodplain wetlands to long-term patterns of flooding and drying and highly variable short-term events. We consider whether the abundance and diversity of fish, macroinvertebrate and zooplankton communities in wetlands of the Coongie Lakes complex are influenced by long-term water regimes. To relate biological changes to changes in water regime, mean values of assemblage indices were ranked and correlated against ranked frequency of drying (i.e. water retention) in each waterbody. As water-retention time increased, fish species diversity (richness, evenness) and disease incidence rose, and fish species dominance and macroinvertebrate abundance decreased. The more mobile species of fish utilised the habitats and food resources provided by newly flooded waterbodies. We conclude that fish populations utilise wetlands with a variety of water regimes, and reductions in the frequency of inundation will decrease fish diversity with sequential losses of less mobile species.J. T. Puckridge, J. F. Costelloe and J. R. W. Rei